That tutorial is about shapes. In general, if an object has any constructors you should use the Metamorph coloring method. I recommend setting the iterator's Map From to Inherit All, so it inherits the pattern from other holons, and usually checking the Inherit Color option to inherit the gradient too. Then you can choose a gradient and adjust meta pattern controls for the constructor. For an introduction to metamorph coloring, look at Metamorph Coloring Basics, section 2.24 (page 68 in the PDF manual).